Crews for contractor Wild Well Control were putting the finishing touches Tuesday on the 100-ton containment dome. A barge at about midday would haul the contraption to the spot 50 miles offshore where a mile-deep gusher from a blown-out undersea well has been spewing at least 210,000 gallons of crude a day into the Gulf for two weeks. BP spokesman John Curry said it would be deployed on the seabed by Thursday.

It’s the latest idea that engineers from oil giant BP PLC were trying since an oil rig the company was operating exploded on April 20, killing 11 workers. It sank two days later, when at least 210,000 gallons per day started pouring into the Gulf. BP is in charge of the cleanup and President Barack Obama and many others say the company also is responsible for the costs.

In their worst-case scenario, BP executives told members of a congressional committee that up to 2.5 million gallons a day could spill if the leaks worsened, though it would be more like 1.7 million gallons.

A rainbow sheen of oil has reached land in parts of Louisiana, but the gooey rafts of coagulated crude have yet to come ashore in most places. Forecasts showed the oil wasn’t expected to come ashore until at least Thursday.

Containment domes have never been tried at this depth — about 5,000 feet — because of the extreme water pressure. The dome, if all goes well, could be fired up early next week to start funneling the oil into a tanker.

“We don’t know for sure” whether the equipment will work, said BP spokesman Bill Salvin. “What we do know is that we have done extensive engineering and modeling and we believe this gives us the best chance to contain the oil, and that’s very important to us.”

The seas calmed Tuesday allowing more conventional methods to contain the spill to get back on track as businesses and residents kept an eye on the ocean currents, wondering when the sheen washing ashore in places might turn into a heavier coating of oil. Crews put out more containment equipment and repaired some booms damaged in rough weather over the weekend. They also hoped to again try to burn some of the oil on the water’s surface, possibly Wednesday.

Across the accident zone, oil floated in the ocean in different hues, shapes and textures. In places, it was a rich paisley patterned reds and oranges. In others, it took on varying gray and blue striated shapes, almost like Vincent Van Gogh’s thick brush strokes.

People along the Gulf Coast have spent weeks living with uncertainty, wondering where and when that huge slick might come ashore, ruining their beaches — and their livelihoods.

The anxiety is so acute that some are seeing and smelling oil where there is none. And even though the dead turtles and jellyfish washing ashore along the Gulf of Mexico are clean, and scientists have yet to determine what killed them, many are just sure the flow of crude unleashed by the explosion at BP’s Deepwater Horizon is the culprit.